Multilayer substrate and method of manufacturing the same

ABSTRACT

A multilayer substrate includes an insulating base member having a plurality of resin films, an electric element embedded in the insulating base member, and a spacer. The resin films are made of a thermoplastic resin and stacked and attached to each other. At least one resin film has a through hole for inserting the electric element. The one resin film further has a plurality of protruding members. One protruding member opposes to another one protruding member so that the one and the another one contact and sandwich the electric element. The spacer is arranged between the one resin film and an adjacent resin film and is disposed at a base portion of one of the protruding members.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-329856filed on Dec. 6, 2006, the content of which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer substrate and a method ofmanufacturing the same.

2. Description of the Related Art

US 2006/0042078 A (corresponding to JP 2006-73763 A) discloses amanufacturing method of a multilayer substrate that includes aninsulating base member and an electronic element embedded in theinsulating base member. In the manufacturing method, the insulating basemember includes a plurality of resin films and a part of the resin filmshas a through hole, in which the electric element is inserted. At leastone of the resin films having the through hole is provided with aplurality of protruding members. The protruding members protrude fromsurrounding portions of the through hole into the through hole. Theprotruding members are arranged so that a distance between opposing tips(top ends) of the protruding members is shorter than an outsidedimension of the electronic element. The electric element is inserted inthe through hole while crushing the tips of the protruding members. Astacked body of the resin films, in which the electric element isarranged, is pressed with heat to form the multilayer substrate.

The electronic element inserted in the through hole is fixed by theresin film having the protruding members, thereby the electronic elementis restricted from getting into an interlaminar of the stacked resinfilms or jumping out from the through hole due to vibrations generatedby inserting another electronic element into an adjacent through hole orcarrying the stacked body to a next process. Thus, the electronicelement is restricted from displacing during a manufacturing process.

According experiments by the inventor of the present application, in acase where the electronic element is out of position with respect to thethrough hole when the electronic element is inserted in the throughhole, the electronic element may chip off the protruding members and maygenerate a resin dust. In addition, the resin dust may affect aconnection between an electrode in the electronic element and aconductive pattern. In contrast, in a case where the electronic elementis positioned with respect to the through hole with a high accuracy, itmay take a long time to inserting the electronic element. Thus, thepositioning of the electric element with a high accuracy is unsuitablefor a case where a plurality of electronic elements is inserted in amultilayer substrate.

It is required to restrict a generation of a resin dust when anelectronic element is inserted in a through hole of stacked resin films,while inserting the electric element in a short time.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide amultilayer substrate. Another object of the invention is to provide amanufacturing method of a multilayer substrate.

According to an aspect of the invention, a multilayer substrate includesan insulating base member, an electric element embedded in theinsulating base member, and a spacer. The insulating base memberincludes a plurality of conductive patterns and a plurality of resinfilms, which is made of a thermoplastic resin and stacked and attachedto each other. The electric includes an electrode electrically coupledwith at least one of the conductive patterns. At least one resin filmhas a through hole in which the electric element is inserted. The oneresin film further has a plurality of protruding members, each of whichprotrudes from a surrounding portion of the through hole into thethrough hole. One protruding member opposes to another one protrudingmember so that the one and the another one contact and sandwich theelectric element. The spacer is disposed between the one resin film andan adjacent resin film, and disposed at a base portion of one of theprotruding members.

In the present multilayer substrate, the spacer is arranged at the baseportion of one of the protruding members, thereby the protruding memberis restricted from being chipped off by the electric element. Thus, themultilayer substrate is restricted from generating a resin dust.

According to another aspect of the invention, a method of manufacturinga multilayer substrate includes a step of preparing a plurality of resinfilms, a step of stacking the resin films and a spacer, a step ofpress-inserting an electric element, and a step of heating and pressingthe stacked resin films. In the step of preparing the resin films, theresin films are made of a thermoplastic resin, and at least one resinfilm has a through hole for inserting an electric element and otherresin film has no through hole. The one resin film further includes aplurality of protruding members, each of which protrudes from asurrounding portion of the through hole into the through hole. Oneprotruding member opposes to another one protruding member so that adistance between top ends of the one and the another one is shorter thanan outside dimension of the electric element. In the step of stackingthe resin films and the spacer, the spacer is arranged between the oneresin film and an adjacent resin film and disposed at a base portion ofone of the protruding members. In the step of press-inserting theelectric element, the electric element is press-inserted in the throughhole by crushing the top ends of the protruding members with theelectric element. In the step of heating and pressing the stacked resinfilms, an insulating base member is formed from the stacked resin filmsand the electric element is embedded in the insulating base member.

In the present manufacturing method, when the electric element isinserted in the through hole, the protruding member pressed by theelectric element may bend from the spacer as a supporting point with alarge bending angle. Thereby, even when the electric element is out ofposition with respect to the through hole, the electric element ispushed toward a center portion of the through hole by a reaction forcefrom the protruding members before the protruding members receive aforce over a break strength of the protruding members. As a result, thepresent manufacturing method restricts a generation of a resin dust dueto inserting of the electric element.

Furthermore, the electric element is fixed by the one resin film havingthe protruding members, thereby the electric element is restricted fromgetting into an interlaminar of the stacked resin films. Therefore, theelectric element is restricted from displacing during a manufacturingprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be morereadily apparent from the following detailed description of preferredembodiments when taken together with the accompanying drawings. In thedrawings:

FIG. 1 is a perspective view showing a process of inserting anelectronic element into a through hole of stacked resin films accordingto a prior art;

FIGS. 2A and 2B are schematic diagrams showing a relationship betweenbending and damaging of a protruding member according to a related artby the inventor of the present application;

FIG. 3 is a schematic perspective view of a protruding member accordingto another related art by the inventor;

FIG. 4 is a schematic cross-sectional view of a multilayer substrateaccording to a first embodiment of the invention;

FIGS. 5A to 5D are cross-sectional views showing a manufacturing processof a resin film to form the multilayer substrate according to the firstembodiment;

FIG. 6 is a plane view of the resin film formed by the manufacturingprocess shown in FIGS. 5A to 5D;

FIG. 7A is a cross-sectional view of a spacer according to the firstembodiment, and FIG. 7B is a plane view of the spacer;

FIG. 8 is a plane view showing a positional relation of the protrudingmembers and the spacer according to the first embodiment;

FIGS. 9A to 9C are cross-sectional views showing a stacking process ofthe resin films and an arranging process of the electronic element;

FIGS. 10A to 10C are cross-sectional views showing the detail of thearranging process of the electronic element;

FIG. 11 is a cross-sectional view showing a heating and pressingprocess;

FIG. 12 is a cross-sectional view showing a stacked body according to amodification of the first embodiment;

FIG. 13 is a plane view of a spacer according to another modification ofthe first embodiment;

FIG. 14 is a cross-sectional view showing a stacking process of resinfilms according to a second embodiment of the invention;

FIG. 15 is a schematic cross-sectional view showing a multilayersubstrate according to the second embodiment; and

FIG. 16 is cross-sectional view showing a stacked resin films accordingto a modification of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A process that the inventor of the present application creates thepresent invention will be described before describing preferredembodiments of the invention.

At first, a multilayer substrate including an insulating base member andan electric element embedded in the insulating base member ismanufactured based on a method disclosed in US 2006/0042078 A(corresponding to JP 2006-73763 A). In the manufacturing method, anelectric element 2 is inserted in a through hole 11 of stacked resinfilms 10 as shown in FIG. 1.

According to experiments by the inventor, in a case where the electronicelement 2 is out of position with respect to through hole 11 when theelectronic element 2 is inserted in the through hole 11, the electronicelement 2 may chip off protruding members 12 from the resin film 10 andmay generate a resin dust. The resin dust (i.e., damage of theprotruding members 12) may generate in a following mechanism.

As shown in FIG. 2A, a friction coefficient between the electronicelement 2 and a pressing member 110 for pressing the electronic element2 into the through hole 11 is determined as “μ”, a bending angle of theprotruding member 12 pressed by the pressing member 110 through theelectronic element 2 is determined as “θ1”, a reaction force of theprotruding member 12 pressed by the electronic element 2 is determinedas “F1”, and a bendable amount of the protruding member 12 is determinedas “V”. Thereby, a horizontal component of the reaction force “F1” isexpressed as “F1·sin θ1”, and a vertical component of the reaction force“F1” is expressed as “F1·cos θ1”. In addition, a frictional forcebetween the pressing member 110 and the electronic element 2 isexpressed as “μ·F1·cos θ1”. Thus, when following formula (1) issatisfied, the electric element 2 is pushed toward a center portion ofthe through hole 11 (i.e., right side in FIG. 2A) due to the reactionforce of the protruding member 12 pressed by the electronic element 2.

F1·sin θ1>μ·F1·cos θ1   (1)

Formula (1) can be replaced with formula (2).

tan θ1>μ  (2)

Thus, the electric element 2 is pushed toward the center portion of thethrough hole 11 when the bending angle “θ1” is large. Specifically, theelectric element 2 is certainly pushed toward the center portion of thethrough hole 11 when θ1≧45°, because the friction coefficient μ<1.

As shown in FIG. 2B, in a case where a deforming amount of theprotruding member 12 reaches the bendable amount “V” without satisfyingthe above formulas (1) and (2), and the protruding member 12 is pressedin a state where the protruding member 12 cannot bend downward any more,a bending angle “θ2” is getting into smaller than the bending angle “θ1”in FIG. 2A. In the present case, a horizontal component “F2·sin θ2” of areaction force “F2” is smaller than a frictional force “μ·F2·cos θ2”between the pressing member 110 and the electronic element 2. Thus, theelectronic element 2 is not pushed toward the center portion of thethrough hole. When the electronic element 2 is provided with a forceover a break strength of the protruding member 12 so that the electricelement is forcibly inserted into the through hole 11, the electricelement 2 may chip off the protruding member 12. In this way, theprotruding member 12 may be damaged.

In another examination by the inventor, the protruding member 12 ismodeled on a cantilever planar triangle, as shown in FIG. 3. When a tipof the protruding member 12 is applied with a load “F”, a bending amount“V(x)” and a bending angle “dV(x)/dx” (=θ) at a point “x” are expressedby following formulas (3) and (4).

V(x)=12L/Eb ₀ h ²(½Fx ² −FLx+½FL ²)   (3)

dV(x)/dx=12L/Eb ₀ h ²(Fx−FL)   (4)

Wherein, “h” is a thickness of the protruding member 12, “L” is a lengthbetween a supporting point and the tip of the protruding member 12, “b₀”is a width of a base portion of the protruding member 12, “bx” is awidth of the protruding member 12 at a point “x”, and “E” is Young'smodulus. When x=0, formulas (3) and (4) are expressed by formulas (5)and (6).

V(0)=6FL ³ /Eb ₀ h ²   (5)

dV(0)/dx=−2V(0)/L   (6)

When the bending amount “V” is constant, the bending angle “dV(x)/dx”(=θ) is expressed as a function of only the length “L” of the protrudingmember 12. Thus, when the length “L” between the supporting point andthe tip of the protruding member 12 is short, the bending angle “θ” islarge, thereby the electric element 2 may be pushed toward the centerportion of through hole 11 before the protruding member 12 is damaged.

First Embodiment

As shown in FIG. 4, a multilayer substrate 100 includes an insulatingbase member 1 and an electric element 2 embedded in the insulating basemember 1. The insulating base member 1 includes a plurality of resinfilms 10 attached each other. For example, the resin films 10 includessix resin films 10 a to 10 f having a thermal plasticity and arranged inorder from top to bottom. The multilayer substrate 100 also includesconductive patterns 3 having a multilayer structure and coupled witheach other through conductive members 4. The conductive members 4 aremade of a sintered conductive paste. The electronic element 2 haselectrodes 2 a coupled with the conductive patterns 3 through theconductive members 4. In the six resin films 10 a to 10 f, four resinfilms 10 b to 10 e arranged between a top resin film 10 a and a bottomresin film 10 f have a through hole 11, for inserting the electricelement 2. Each of the four resin films 10 b to 10 d has a plurality ofprotruding members 12 protruding from surrounding portions of thethrough hole 11 shown by dotted lines C in FIG. 4 into the through hole11. One protruding member 12 opposes to another one protruding member 12so that the one and the another one contact and sandwich the electricelement 2. The protruding members 12 are integrated with the insulatingbase member 1.

The multilayer substrate 100 further includes a plurality of spacers 20having a certain thickness. The spacers 20 are arranged between each ofthe resin films 10 b to 10 e. Specifically, the spacers 20 are arrangedat base portions of the protruding members 12. In the present example, amaterial of the spacers 20 is different with those of other componentsin the multilayer substrate 100 but has a similar linear-expansioncoefficient. Additionally, the spacers 20 are thinner than the resinfilms 10 a to 10 f.

A manufacturing method of the multilayer substrate 100 will now bedescribed with reference to FIGS. 5A-11. At first, a manufacturingprocess of the resin film 10 b will be described with reference to FIGS.5A-6. As shown in FIG. 5A, a metal film is attached to a surface of afilm 1 a made of a thermoplastic resin such as a liquid crystal polymerand is patterned by photolithography and etching to form the conductivepatterns 3. As a thermoplastic resin for a material of the film 1 a,polyether ether ketone (PEEK), polyetherimide (PEI), and polyether etherketone (PEEK)/polyetherimide (PEI) composite and the like may be usedinstead of the liquid crystal polymer. A preferred metal film for theconductive patterns 3 is copper film, which has a high electricconductivity and a high strength.

Next, as shown in FIG. 5B, the through hole 11 is provided in the film 1a by laser processing. When the through hole 11 is provided, theprotruding members 12 are formed to protrude from the surroundingportions shown by the dotted lines C into the through hole 11, as shownin FIG. 6. One protruding member 12 opposes to another one protrudingmember 12. In the present example, opposing two pairs of protrudingmembers 12 (i.e., four protruding members 12) are formed. In addition,the through hole 11 and the protruding members 12 are formed so that adistance W1 between top ends of the opposing protruding members 12 isshorter than an outside dimension of the electric element 2. Theprotruding members 12 may have various shapes. In a case where theprotruding members 12 have approximately triangle planar shapes, springconstants are smaller than a case where the protruding member 12 haveapproximately rectangular planar shapes when the distance W1 and a sizeof the through hole 11 are almost same in both of the cases. Therefore,when the protruding members 12 have approximately triangle planarshapes, the electric element 2 is easily inserted into the through hole11.

After providing the through hole 11, bottomed holes 13 are provided bylaser processing, as shown in FIG. 5C. The bottomed holes 13 arebottomed with the conductive patterns 3. Then, a conductive paste 4 isfilled in the bottomed holes 13 by a screen-printing method. When theconductive paste 4 is filled in the bottomed holes 13, protective filmsmay be attached to an upper surface and a lower surface of the film 1 ato restrict a pollution of the film 1 a by the conductive paste 4 and adamage of the conductive patterns 3, and may remove the protective filmsafter filling the conductive paste 4.

The resin films 10 c to 10 e are formed by manufacturing processessimilar with that of the resin film 10 b. In addition, the resin films10 a and 10 f are made by the manufacturing process of the resin film 10b without providing the through hole 11 as shown in FIG. 5B.

The spacers 20 are formed separately from the resin films 10 a to 10 f.When the multilayer substrate 100 is formed, the spacers 20 are arrangedbetween at least one of the resin films 10 b to 10 e having theprotruding members 12 and an adjacent resin film in a direction that theelectric element 2 is inserted. Furthermore, the spacers 20 are arrangedat the base portions of the protruding members 12. Thereby, the spacers20 function as supporting points of the protruding members 12 when theprotruding members 12 are deformed elastically by receiving a force fromthe electric element 2 in an arranging process of the electric element2. Thus, the protruding members 12 may be made of various materials thatcan function as the supporting points. In the present example, thespacers 20 are made of a resin film that is restricted from fluidizingin a heating/pressing process and has a similar linear-expansioncoefficient with those of the films 1 a. In addition, the spacers 20 arethinner than the films 1 a (i.e., the resin films 10 a to 10 f). Asshown in FIGS. 7A and 7B, the spacers 20 are formed into approximatelyrectangular ring shapes by punching the resin films, thereby the spacers20 correspond to the base portions of the four protruding members 12 asshown in FIG. 8.

Then, the resin films 10 a to 10 f and the spacers 20 are stacked andthe electric element 2 is inserted. Specifically, as shown in FIG. 9A,the resin films 10 b to 10 f are positioned so that the through holes 11provided in the resin films 10 b to 10 f are connected to form a concavepart for inserting the electric element 2 therein. At this time, thespacers 20 are arranged between each of the resin films 10 b to 10 e andadjacent to the through hole 11. Thus, in the four resin films 10 b to10 e having the protruding members 12, upper three resin films 10 b to10 d, in which the electric element 2 is inserted before the resin film10 e, are used for restricting a displacement of the electric element 2,i.e., centering of the electric element 2. The protruding members 12 ofthe resin film 10 e, which are not used for restricting a displacementof the electric element 2, are used with the protruding members 12 ofthe resin films 10 b to 10 d, for fixing the electric element 2 afterinserting, and covering the electric element 2 after heating andpressing.

In the present example, the four resin films 10 b to 10 e have thethrough hole 11. However, the number of stacked resin films having thethrough hole 11 may be determined in accordance with a height of theelectric element 2. In addition, the number of stacked spacers 20 may bedetermined in accordance with the number of the resin films having theprotruding members 12 used for restricting the displacement of theelectric element 2.

Next, the electric element 2 is pressed into the through hole 11provided with the protruding members 12 while crushing the top ends ofthe protruding members 12, as shown in FIG. 9B. As shown in FIG. 10A,the distance W1 between the top ends of the protruding members 12 of theresin films 10 b to 10 e are set to be shorter than the outsidedimension W2 of the electric element 2. In addition, the spacers 20 arearranged at the base portions of the protruding members 12. Thus, whenthe electric element 2 is inserted into the through hole 11 by pressedby the pressing member 110, the protruding member 12 pressed by theelectric element 2 are elastically deformed from adjacent spacers 20 asthe supporting points with a large bending angle “θ” as shown in FIG.10B. Thereby, even when the electric element 2 is out of position withrespect to the through hole 11 as shown in FIG. 10A, the electricelement 2 is pushed toward the center portion of the through hole 11 bya horizontal component of a reaction force from the protruding members12 before the protruding members 12 receive a force over the breakstrength of the protruding members 12, as shown in FIG. 10B. As aresult, the electric element 2 is arranged in the through holes 11. Inthis way, the protruding members 12 are restricted from damaging due toinserting of the electric element 2, and the multilayer substrate 100restricts a generation of a resin dust.

In the present example, the protruding members 12 are formed so that thefriction coefficient “μ” between the pressing member 110 and theelectric element 2 and the bending angles “θ” of the protruding members12 satisfy the above-described formula (2). Thus, even when the electricelement 2 is out of position with respect to the through hole 11, theelectric element 2 is pushed toward the center portion of the throughhole 11 by the horizontal component of the reaction force from theprotruding members 12 before the protruding members 12 receives a forceover the break strength of the protruding members 12.

As shown in FIG. 9B and 10C, the electric element 2 inserted into theconcave part provided by the connected through holes 11 is fixed by theresin films 10 b to 10 e having the protruding members 12. Thus, theelectronic element 2 is restricted from getting into an interlaminar ofthe stacked resin films 10 or jumping out from the concave part due tovibrations generated by inserting another electronic element (not shown)into an adjacent through hole (not shown) or carrying a stacked body toa next process.

After the electric element 2 is arranged, the resin film 10 a withoutthe through hole 11 is stacked on the stacked body including the resinfilms 10 b to 10 f, as shown in FIG. 9C.

The stacked body including the resin films 10 a to 10 f, the electricelement 2, and the spacers 20 is put between a pair of heat pressingplates 120 having heaters. Then, the stacked body is heated and pressedby the heat pressing plates 120 from the both sides. A preferred appliedpressure is about 4 MPa. A preferred heating temperature is about in arange from 300 to 350° C. when the thermoplastic resin films 1 a aremade of a liquid crystal polymer. When the stacked body is heated andpressed, the thermoplastic resin films 1 a are softened. Thereby, theresin films 10 a to 10 f are attached to each other so that theinsulating base member 1 is formed. In addition, clearances around theelectric element 2 are entirely filled with flowing films 1 a, therebythe electric element 2 is embedded in the insulating base member 1.Furthermore, when the stacked body is heated and pressed, the conductivepaste 4 is sintered so that the conductive members 4 for electricallycoupling the conductive patterns 3 are formed. In this way, themultilayer substrate 100 shown in FIG. 4 is formed.

The present manufacturing method of the multilayer substrate 100restricts a generation of a resin dust when the electric element 2 isinserted. Thus, the multilayer substrate 100 manufactured by the presentmethod restricts a poor connection between the electrodes 2 a of theelectric element 2 and the conductive patterns 3. According toexperiments by the inventor, it is confirmed that, when the electricelement 2 is intentionally displaced with respect to the through hole 11when the electric element 2 is inserted into the through hole 11, thepresent manufacturing method restricts a generation of a resin dustcompared with the manufacturing method according to the prior art.

In addition, the present manufacturing method restricts the electricelement 2 from getting into an interlaminar of the stacked resin films10 b to 10 f, thereby a displacement of the electric element 2 in themanufacturing process is restricted. Furthermore, the presentmanufacturing method restricts a generation of a resin dust, thereby aplurality of electric elements 2 can be inserted in a short time using ahigh speed mounter.

The spacers 20 are thinner than the resin films 10 a to 10 f in adirection that the resin films 10 a to 10 f are stacked, thereby stepsdue to the spacers 20 are easily filled with the softened films 1 a.Thus, clearances remaining in the insulating base member 1 are reducedwhen the multilayer substrate 100 is formed.

In the above-described example, all of the resin films 10 b to 10 ehaving the through hole 11 are provided with the protruding members 12,and the spacers 20 are arranged between each of the films 10 b to 10 e.Alternatively, at least one of the resin films 10 having the throughhole 11 may be provided with the protruding members 12, and the spacer20 may be arranged between the resin film having the protruding members12 and an adjacent film. For example, as shown in FIG. 12, in four resinfilms 10 b to 10 e having the through hole 11, only the resin film 10 bmay be provided with the protruding members 12, and the spacer 20 may bearranged between the resin films 10 b and 10 c. The spacer 20 in FIG. 8has the approximately rectangular shape, which surrounds the throughhole 11 and corresponds to the base portions of the four protrudingmembers 12. The spacer 20 is required to be arranged at the baseportions of the protruding members 12 so that the spacer 20 functions asthe supporting points of the protruding member 12. Thus, as shown inFIG. 13, a plurality of spacers 20 may be independently arranged at thebase portions of the protruding members 12, for example.

Second Embodiment

In the multilayer substrate 100 in FIG. 4, the material of the spacers20 is different with those of other components in the multilayersubstrate 100. Alternatively, the spacers 20 may be made of the samematerial as one of the other components.

For example, as shown in FIG. 14, spacers 21 made of the samethermoplastic resin (e.g., liquid crystal polymer) as the films 1 a maybe used as the spacers 20. The spacers 21 are formed by punching of athermoplastic resin film, which is thinner than the films 1 a. Thespacers 21 have similar shapes with those of the spacers 20.

In a case where the spacers 21 and the films 1 a are made of the samematerial, when the resin films 10 a to 10 f are attached to each otherto form the insulating base member 1 in the heating and pressingprocess, the spacers 21 are also softened and attach to adjacent films10, as shown in FIG. 15. Thus, a connection reliability between thespacers 21 and the resin films 10 increases.

In addition, the spacers 21 are softened and flow, thereby clearancesremaining in the insulating base member 1 are effectively reduced whenthe multilayer substrate 100 is formed.

Furthermore, the resin films 10 and the spacers 21 are formed separatelybut are made of the same material. Thus, the multilayer substrate 100has a simple structure.

Alternatively, the spacers 20 may be made of the same material as one ofother components without limiting the films 1 a. For example, as shownin FIG. 16, the spacers 22 made of the same material as the conductivepatterns 3 may be used as the spacers 20. Specifically, the spacers 22as dummy patterns, which are not coupled with the conductive patterns 3,are arranged on upper surfaces of resin films 10 c to 10 e in additionto the conductive patterns 3. The spacers 22 are formed at the same timeas the conductive patterns 3. The spacers 22 are integrated with theresin films 10 c to 10 e and are not required to be formed separately,thereby the multilayer substrate 100 has a simple structure.Alternatively, a part of the conductive patterns 3 may function as thespacers 22.

Other Embodiments

In the electric element arranging process shown in FIGS. 10A-10C, theelectric element 2 is inserted into the concave part of the stacked bodyin a state where the resin films 10 b to 10 f and spacers 20 arestacked. Alternatively, the electric element 2 may be inserted in astate where the resin films 10 b to 10 f and the spacers 20 are attachedtemporarily. In the present case, the stacked resin films 10 b to 10 fare fixed to each other when the electric element 2 is inserted, therebythe electric element 2 is restricted from getting into an interlaminarof the stacked resin films 10 b to 10 f due to vibrations generated byinserting the element 2 and carrying the stacked body to a next process.The resin films 10 b to 10 f and the spacers 20 are attached temporarilyby putting the stacked body between the heat pressing plates 120 andheating and pressing the stacked body with a lower temperature and alower pressure compared with the heating and pressing process in FIG.11. A preferred applied pressure is about 2 Mpa. A preferred heatingtemperature is about in a range from 200 to 250° C. when the films 1 aare made of a liquid crystal polymer.

Such changes and modifications are to be understood as being within thescope of the present invention as defined by the appended claims.

1. A multilayer substrate comprising: an insulating base memberincluding a plurality of conductive patterns and a plurality of resinfilms, which is made of a thermoplastic resin and stacked and attachedto each other; an electric element embedded in the insulating basemember and including an electrode electrically coupled with at least oneof the conductive patterns; and a spacer, wherein: at least one resinfilm has a through hole in which the electric element is inserted; theone resin film has a plurality of protruding members, each of whichprotrudes from a surrounding portion of the through hole into thethrough hole; one protruding member opposes to another one protrudingmember so that the one and the another one contact and sandwich theelectric element; and the spacer is disposed between the one resin filmand an adjacent resin film, and disposed at a base portion of one of theprotruding members.
 2. The multilayer substrate according to claim 1,wherein: the spacer is thinner than one resin film in a stackingdirection of the plurality of resin films.
 3. The multilayer substrateaccording to claim 1, wherein: the spacer is provided by one of theconductive patterns.
 4. The multilayer substrate according to claim 1,wherein: the spacer is made of the same thermoplastic resin as theplurality of resin films.
 5. The multilayer substrate according to claim1, wherein: the spacer has an approximately rectangular ring shapesurrounding the through hole.
 6. The multilayer substrate according toclaim 1, wherein: the spacer includes a plurality of spacer elements,each of which corresponds to one of the protruding members and isarranged at a base portion of the one of the protruding members.
 7. Amethod of manufacturing a multilayer substrate, comprising: preparing aplurality of resin films made of a thermoplastic resin, wherein at leastone resin film has a through hole for inserting an electric element andother resin film has no through hole, and the one resin film furtherincludes a plurality of protruding members, each of which protrudes froma surrounding portion of the through hole into the through hole, andwherein one protruding member opposes to another one protruding memberso that a distance between top ends of the one and the another one isshorter than an outside dimension of the electric element; stacking theresin films and a spacer, wherein the spacer is arranged between the oneresin film and an adjacent resin film and disposed at a base portion ofone of the protruding members; press-inserting the electric element inthe through hole by crushing the top ends of the protruding members withthe electric element; and heating and pressing the stacked resin filmsso that an insulating base member is formed from the stacked resin filmsand the electric element is embedded in the insulating base member. 8.The method of manufacturing a multilayer substrate according to claim 7,wherein: the stacking of the resin films includes temporarily attachingthe resin films to each other by heating and pressing the stacked resinfilms; the press-inserting of the electric element includes arrangingthe electric element in the through hole of the temporary attached resinfilms; and the heating and pressing of the stacked resin films includesheating and pressing the temporary attached resin films.
 9. The methodof manufacturing a multilayer substrate according to claim 7, wherein:the spacer is thinner than one resin film in a stacking direction of theplurality of resin films.
 10. The method of manufacturing a multilayersubstrate according to claim 7, wherein: the stacking of the resin filmsincludes stacking conductive patterns with the resin films; at least oneof the conductive patterns is electrically coupled with the electricelement; and the spacer is provided by another one of the conductivepatterns.
 11. The method of manufacturing a multilayer substrateaccording to claim 7, wherein: the spacer is made of the samethermoplastic resin as the plurality of resin films.
 12. The method ofmanufacturing a multilayer substrate according to claim 7, wherein: thepreparing of the resin films includes forming each protruding member tobe an approximately triangle planar shape.
 13. The method ofmanufacturing a multilayer substrate according to claim 7, wherein: afriction coefficient between the electric element and a pressing memberfor pressing the electric element into the through hole is defined as μ;a bending angle of the protruding member while pressed by the pressingmember is defined as θ; and the preparing of the resin films includesforming the protruding members so that the friction coefficient and thebending angle satisfy a following formula of tan θ>μ in thepress-inserting of the electric element.